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DNA Binding by a New Metallointercalator that Contains a Proflavine Group Bearing a Hanging Chelating Unit
Author(s) -
Bazzicalupi Carla,
Bencini Andrea,
Bianchi Antonio,
Biver Tarita,
Boggioni Alessia,
Bonacchi Sara,
Danesi Andrea,
Giorgi Claudia,
Gratteri Paola,
Ingraín Antonio Marchal,
Secco Fernando,
Sissi Claudia,
Valtancoli Barbara,
Venturini Marcella
Publication year - 2007
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200601855
Subject(s) - chemistry , intercalation (chemistry) , protonation , proflavine , moiety , dna , crystallography , acridine , stereochemistry , chelation , inorganic chemistry , organic chemistry , ion , biochemistry
The new bifunctional molecule 3,6‐diamine‐9‐[6,6‐bis(2‐aminoethyl)‐1,6‐diaminohexyl]acridine ( D ), which is characterised by both an aromatic moiety and a separate metal‐complexing polyamine centre, has been synthesised. The characteristics of D and its Zn II complex ([Zn D ]) (protonation and metal‐complexing constants, optical properties and self‐aggregation phenomena) have been analysed by means of NMR spectroscopy, potentiometric, spectrophotometric and spectrofluorimetric techniques. The equilibria and kinetics of the binding process of D and [Zn D ] to calf thymus DNA have been investigated at I =0.11 M (NaCl) and 298.1 K by using spectroscopic methods and the stopped‐flow technique. Static measurements show biphasic behaviour for both D –DNA and [ ZnD ]–DNA systems; this reveals the occurrence of two different binding processes depending on the polymer‐to‐dye molar ratio ( P / D ). The binding mode that occurs at low P / D values is interpreted in terms of external binding with a notable contribution from the polyamine residue. The binding mode at high P / D values corresponds to intercalation of the proflavine residue. Stopped‐flow, circular dichroism and supercoiled‐DNA unwinding experiments corroborate the proposed mechanism. Molecular‐modelling studies support the intercalative process and evidence the influence of NH + ⋅⋅⋅O interactions between the protonated acridine nitrogen atom and the oxygen atoms of the polyanion; these interactions play a key role in determining the conformation of DNA adducts.